Without limiting the scope of the invention, its background is described in connection with current methods of forming metal interconnects and other metal structures within integrated circuits, as an example.
Heretofore, in this field, polycrystalline aluminum has been widely used for metallization in integrated circuits because of its high conductivity, pattern-ability, good adherence and bondability, low cost, easy availability and ease of deposition. However, polycrystalline aluminum has poor electromigration resistance and can intermix with silicon. To solve these problems, small amounts of copper and silicon are added into the polycrystalline aluminum. The copper, however, makes the metal alloy difficult to plasma etch ant the silicon can precipitate and thus increase the electrical resistance of the metal path.